Last week I finished up the review of the Sony VAIO Pro 13, which delivers excellent battery life compared to most other laptops that we’ve tested – granted, it’s also one of the first Haswell ULT systems we’ve tested as well. Shortly after the review posted, Microsoft officially released the Windows 8.1 update. Battery life is apparently one of the areas that’s supposed to improve with Windows 8.1, or at least that’s the theory. I reran the battery life tests (only with the internal battery, in order to keep testing time manageable), and here are the results:

Sony VAIO Pro 13 Battery Life (Minutes)

Windows 8

Windows 8.1

Light

481

479

Medium

315

283

Heavy

195

191

I’m going to have to rerun the Medium test (after the battery finishes recharging yet again), just to verify the result, as it shows a rather significant 11% drop compared to my initial testing. (Update: a second run confirms it; I don't know why, but the Medium test is definitely getting worse battery life now.) As for the other two tests, they’re also down compared to the earlier results, but here we see a 2% drop in the Heavy test and only a 0.4% drop in the Light result. A margin of error of ~2% is normal for battery life testing, so short of retesting multiple times I’m willing to call the Light and Heavy results a tie.

The main takeaway here is that anyone expecting Windows 8.1 to dramatically improve battery life relative to Windows 8 is likely going to be disappointed. Note that we do test with the LCD at a constant 200 nits, so optimizations that turn off the display sooner rather than later could still have an impact, but in comparing equivalent settings we did not notice any improvement on the VAIO Pro 13.

Far more important in my experience will be the laptop BIOS/firmware. I’ve been communicating with Intel recently in the hope of helping to improve the situation, as I have a few Haswell-equipped laptops that are failing to deliver the expected battery life. If all goes well, Intel will bang some OEM heads and we’ll get BIOS updates that will improve our battery life.

Frankly, I’m amazed that some companies still appear to not put in the necessary time/effort to deliver good battery life. Clevo is probably my biggest gripe right now, and we’ve dinged them on battery life for as long as I can remember. With the Haswell Clevo notebooks that I have right now (P157SM and W740SU), it appears neither one is using the deeper sleep states (C6/C7) for the CPU package – and in the case of the P157SM, it’s not even using the package C3 state. The CPU cores are properly using C7, but the package is not. That may not be the only item holding back battery life, but at least it appears to be part of the puzzle.

In short, consider this a warning shot across the bow of the laptop manufacturers. It’s time to join the modern world, and failing to put unused devices to sleep or to take advantage of deeper sleep states with computer hardware is not acceptable, especially on a laptop. I don't want software hacks to turn off the display more quickly, or drop the brightness to 100 nits in direct sunlight; I want real improvements. Besides raw battery life, I'll at least be checking to see that future laptops use all the available C-states (on the cores as well as the CPU package) when running off the mains.

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33 Comments

I'd like to request an article/chart of haswell laptops and C-state support much like you made recently for mobile device test suite cheats. It's a lot of work but I think it paints a clear picture for consumers and sends a strong message to OEMs. At the very least it makes choosing a laptop easier.Reply

I can provide charts for the Haswell laptops we still have on hand, but most of the previously tested laptops have already been returned. I'll see about doing a follow-up to this post perhaps later today....Reply

It just occurred to me, as I don't recall seeing this information in your reviews, but when testing battery life, I assume you do so through the desktop on Windows 8(.1)? Or with the desktop open at least?It would be nice to know if the battery tests would come out differently if one stayed entirely in the Modern UI (as that would intuitively be the case given the lack of resource control on the desktop).Staying in Modern doesn't make much sense on a laptop necessarily, but it's something that's nice to know for x86 hybrids (Surface Pro 2 being a prime candidate). :-)

The benchmarks we run do use IE10 (now IE11) in desktop mode. I can try doing a test using the IE Win8 app, but actually when Win8 first appeared I did a battery life test and the non-desktop IE10 delivered worse battery life. I think the Modern UI may actually put a constant (albeit small) load on the iGPU that's more demanding in terms of power than the desktop.Reply

It would certainly be nice to know if that is still the case in IE11 and 8.1, and I would also be interested in knowing if it's the case with something like video playback. Just for accuracy's sake. :-)Reply

It will obviously take a bit of time to test, but I'll look into it. I think it might be a good time to do some pure video testing as well using MPC-HC, VLC, Windows Media Player, and the new Video app to see which does best in terms of battery life. It will take about a week, give or take, before I can test all those....Reply

Jarred: Just as a sidenote, Sony is using heavily modified drivers for their Vaio Laptops and I would therefore take the above posted results with a grain of salt as long as there are no "real" Windows 8.1 drivers for the Sony Vaio Pro 13. Other than that I do agree on your statement that PC OEMs definitely need to step up their drivers and continued support.Reply